so, I stopped doing this in '88

and things are a bit different now. I have a few questions if you guys will help me out. I bought a cruiser and started racing again last weekend, and my issues are:
Why are the stock tires so big? 1.95?!? I looked around and everyone is racing large tires. Is it uncommon for me to throw the 1 3/8 on here?
why is my sprocket so small? This dk came stock with a 30 - I always used a 44. Is this normal?
Are people going to throw things at me if I put Pro bars on a cruiser? These feel a bit small with a 5" rise.

I'll keep quiet for the most part, glad to be here, and thanks in advance for any help.

Some spin some don't. With that said... different tracks require different gearing.... DK didn't know what track you were going to be riding on. They didn't know how long the straights were, or how long the whole track was. I too ran a 44t on my old Cycle Craft back in the day... but I mashed like crazy compared to the other riders. I prefered to carry the speed than to spin my azz off, brake hard, just to sprint again. I was better at taking high corners and powering through, or entering high, and cutting low using the berm as a down hill.... worked for me even if it wasn't "conventional" or the normal.

Tires... seemed to go by fads if I remember correctly.... honestly, lighter is better as long as you have plenty of sidebite... I only raced a select few races which were mud-fests and would benefit from a wider tire. Man were those fun.... unfortunatly I was on skinny Junior sized tires at the time... talk about "spinning" up the jumps... literally.

I race cruiser as well so will offer my opinion.
What size sprocket you run doesn't matter unless you are a weight weenie. It is the resulting gear ratio that matters. The gear ratio is influenced by your tires, sprocket and cog, most cruiser racers I know run somewhere between 54 and 58 gear inches. If you run a 44 on the front you would need to run a 19 tooth sprocket on the back to get in this range, I ran 44 * 18 for awhile, that gave me 58.5 gear inches with my 1.85 tires,but I was getting killed out of the gates. I now run 40 * 17 for 56.5 gear inches, I tried 39 * 17 but felt off balance with my feet going so fast. If you start messing with the sprockets and cogs you will need to either run a long chain and a tensioner (not a tug) or have numerous chains that go with each combo.
Tire size is a matter of preference. I like a lot of air volume as I am a terrible jumper/lander but a lot of the faster guys at the local tracks run 1.5's. If you go to the smaller tires then your gear inches will drop as well.
I tried the pro bars on my cruiser as I am 6'7" and felt wierd with the lower bars. The tall bars felt equally as wierd and made the bike feel twitchy. I have just put on some 6 inch rise to try out but that will have to wait as I broke a few ribs trying to learn to jump better.

Terminology issue with "Chain tensioners".
Some are as wethepeople indicated, they pull the wheel back in the dropout and keep it there. What I was referring to was a spring loaded one that has a pulley that your chain runs over, this type of tensioner takes up slack in the chain. Similar to the one in the link

The beauty of this on a cruiser is that you can run a chain that is a bit long so that you are able to change sprockets/cogs without having to change the chain. It also makes tight spots in your driveline not a problem.

Tire size changes the gear ratio as the narrower tire has a smaller diameter.